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Many efforts have been made in recent years to find renewable replacements for fossil fuels that can reduce the carbon footprint without compromising combustion performance. Bio-blendstock oil developed from woody biomass using a reliable thermochemical conversion method known as catalytic fast pyrolysis (CFP), along with hydrotreating upgrading has the potential to deliver on this renewable promise. To further our understanding of naphthenic-rich bio-blendstock oils, an improved formulation surrogate fuel (SF), SF1.01, featuring decalin and butylcyclohexane naphthenic content was devised and blended with research-grade No.2 diesel (DF2) at various volume percentages. The blends were experimentally evaluated in a single-cylinder Ricardo Hydra compression ignition engine to quantify engine and emissions performance of SF1.01/DF2 blends. Injection timing events were varied from knock limit to misfire limit at the same operating conditions for all blends.

Homogeneous Charge Compression Ignition (HCCI) enables combustion with high efficiency and low emissions. Control over the combustion process and its narrow operating range are still the biggest challenges associated with HCCI. To expand the operable load ranges of HCCI, this paper explores the effects of single versus two-stage ignition fuels by studying the Primary Reference Fuels (PRF) in a variable compression ratio Cooperative Fuel Research (CFR) engine. The PRF fuels, iso-octane and n-heptane, are blended together at various concentrations to create fuel blends with different autoignition characteristics. Experiments were conducted using these PRF blends to explore the extent to which the load range can be extended with two-stage ignition fuels at various compression ratios and intake temperatures. The reactivity of the PRF blends increases with the fraction of n-heptane and so does the amount of low temperature heat release (LTHR).

This article investigates the effects of various primary reference fuel (PRF) blends, compression ratios, and intake temperatures on the thermodynamics and performance of homogeneous charge compression ignition (HCCI) combustion in a Cooperative Fuels Research (CFR) engine. Combustion phasing was kept constant at a CA50 phasing of 5° after top dead center (aTDC) and the equivalence ratio was kept constant at 0.3. Meanwhile, the compression ratio varied from 8:1 to 15:1 as the PRF blends ranged from pure n-heptane to nearly pure isooctane. The intake temperature was used to match CA50 phasing. In addition to the experimental results, a GT-Power model was constructed to simulate the experimental engine and the model was validated against the experimental data. The GT-Power model and simulation results were used to help analyze the energy flows and thermodynamic conditions tested in the experiment.